Teaching apparatus

ABSTRACT

A teaching apparatus has a student-answer registering device including a number of individually manipulatable keys bearing different marks, with the device indicating a correct student answer on manipulation of any key the mark of which is in the order of the same key mark in a preassigned recurring sequence of successive manipulations of the keys, and the apparatus being adapted for use with successive cards or the like of which each card displays a problem question and as many answers thereto, including one correct one, as there are keys, with the answers on each card being marked the same as the keys, and the marks applied to the correct answers on successive cards conforming to the preassigned key mark sequence.

United States Patent lnventor William 1!. Lyon Woodbridge, Conn. Appl.No. 817,803 Filed Apr. 21, 1969 Patented May 4, 1971 Assignee KMSIndustries, Inc.

Ann Arbor, Mich.

TEACHING APPARATUS 20 Claims, 18 Drawing Figs.

11.8. C1 35/9 35/6 Int. Cl G09b 3/06 Field of Search 35/9, 6, 9.1

References Cited UNITED STATES PATENTS Re23,030 8/1948 Holt 35/9X1,749,226 3/1930 Pressey 35/9 ABSTRACT: A teaching apparatus has astudent-answer registering device including a number of individuallymanipulatable keys bearing different marks, with the device indicating acorrect student answer on manipulation of any key the mark of which isin the order of the same key mark in a preassigned recurring sequence ofsuccessive manipulations of the keys, and the apparatus being adaptedfor use with successive cards or the like of which each card displays aproblem question and as many answers thereto, including one correct one,as there are keys, with the answers on each card being marked the sameas the keys, and the marks applied to the correct answers on successivecards conforming to the preassigned key mark sequence.

i l P EAN PANE i PAIN PATENTEUQHAIY 4m 3577.656

SHEETIUFG INVENTOR BY L I W I A ORNEY PATENT ED MAY 4 IQTI SHEET 2 0F 6EXT WHICH WORD MEANS ACHE INVENTOR MY/Z'G/fl A. Lyon BY PATENTIEDHAFY:419?:

sum 5 OF 6 E5005 @jm rsAcruNo APPARATUS to teaching apparatus of thequestion-and-answer kindin particu'lar.

The present invention is concerned with the type of teaching apparatusemploying cards or the like with problem questions, and having scoremechanism selectively operable by a student to register his or heranswers from an available list of answers, including only one correctone,to each question and to record the correctness or incorrectness ofthe registered answers.

It is among the objects of the present invention to provide teachingapparatus of this type in which a series of question cards or the likeare insertable, and which has score mechanism with selectively operableregistration" keys which are individually associated with the answerson-an available list of answers to the question on each card, and whichon manipulation by a student register the associated listed answers,with successive ones of the cards being displayed for the studentsconsideration and answer selection only if the students registeredanswer to' the question on the preceding card is the correct one. Withthis arrangement, the

student is immediately aware of the correctness or incorrectnes of hisor her registered answer to the question on any card by the ensuingdisplay or lack of display, respectively, of the next card, and thestudent will on registration of any incorrect answer have theopportunity to again ponder the same question and registerthe correctanswer or another incorrect answer.

It is another object of the present invention to provide teachingapparatus of this type which, in addition to giving the aforementionedimmediate indication to thestudent of any registered correct orincorrect answer, also keeps visible and tarnperproot" score of thenumber of registered wrong answers to the questions on'an entire seriesof inserted cards, thereby to permit grading of the students effort by asupervisor and/or by the student himself or herself. To this end, theapparatus has a score mechanism which is actuated on each manipulationof a registration key that registers an incorrect answer.

It is a further object of the present invention to provide teachingapparatus of this type which has provisions, preferably an index" key,for clearly marked student manipulation to cause display of the nextcard without prior registration of any student answer. With thisarrangement, the apparatus is adaptable for insertable series of cardsof which each series has an explanatory card or cards that bearexplanations or instructions relative to a question or questions on asucceeding card or cards and, hence, require no student answer.

Another object of the present invention is to provide teaching apparatusof this type in which the aforementioned index key is also associatedwith the score mechanism so that on each manipulation of this index keythe mechanism is actuated to score an incorrect answer. arrangementintroduces a unique feature in that a student not knowing the correctanswer to the question on any particular card and scheming to avoid apossible incorrect answer score by not manipulating any of theregistration keys and instead manipulating the index key, will notsucceed in this because manipulation of the index key does entail anincorrect answer score. On the other hand, the true score of registeredincorrect answers to all questions on the cards of a series including anexplanatory card or cards is readily obtained by simply deducting fromthe indicated score the designated number of such explanatory cards.

A further object of the present invention is to arrange each seriesofcards intended for apparatus ofthis type so that each question cardbears, besides a specific question, also the aforementioned listedarswers, preferably more than two, to the specific question, and theapparatus is coordinated with the insertable card series by having asmany answer registration keys as there are answers on each questioncard, and each of these registration keys is further coordinated with aparticular selected one. of these keys the student registers thecoordinated answer on the card which he or she'believes to be thecorrect answer. i

It is another object of the present invention to achieve theaforementioned coordination between the registration keys of theapparatus and the answers given on any displayedquestion card of aninserted card series by the simple expediency of marking the answers oneach question card with distinguishing characters and marking theregistration keys with the same distinguishing characters, with eachregistration key being marked with the same character as the answer onany card with which it is coordinated.

It is a further object of the present invention to provide teachingapparatus of this type which for display or nondisplay of successivecards pursuant to each prior student registration of a correct orincorrect answer, respectively, has as its primary operating elements agroup of coaxial discs turnable in unison and being in number equal tothe number of registration keys, of which each disc has a peripheralshoulder and all shoulders are equiangularly spaced from each other,with one shoulder being in a predetermined angular operating position,and there is associated with each registration key and a disc a pawlwhich on manipulation of the key is moved into register with theshoulder on the associated disc if that shoulder is in the predeterminedangular operating position, and any pawl registering with the shoulderon the associated disc indexing all'discs through one step equal to thedistance between successive shoulders, with the next card beingdisplayed on each indexing step of the discs. With this arrangement, afixed sequence of manipulation of the registration keys for registeringsuccessive correct answers is built in the apparatus, with this sequencebeing as the chosen, i.e., programmed, sequence of the associated discswhose shoulders'follow each other into the'predetermined angularoperating position. Therefore, the aforementioned distinguishing markson the correct answers to questions on successive cards must not onlyfollow each other in the same sequence as the same marks on theregistration keys which on successive manipulation register successivecorrect answers, but must also be in step with the marks on these keysin the sense that on manipulation of any registration key with aparticular mark for registration of a correct answer the registeredanswer will indeed conform to the identically marked, correct one of theanswers to the question on the then displayed card,

Another object of the present invention is to provide teaching apparatusof this type in which the aforementioned sequence of manipulation of theregistration keys for registration of successive correct answers, andwith it the sequence of the marks on the correct answers on successivecards,.is prolonged quite appreciably, by the simple expediency ofproviding the discs with an overall number of shoulders greater than thenumber of discs. With this arrangement, the sequence of key manipulationfor successive correct-answer registrations, while recurring, maynevertheless be sufficiently prolonged to escape detection by most anystudent, and the same single key manipulation sequence mayadvantageously be built into all apparatus of this type fortheirsimplified and low-cost production.

It is another object of the present invention to provide teachingapparatus of this type which visually indicates by different marks themanipulation of successive keys in the aforementioned sequence of keymanipulations, whereby a sequence of key manipulations may be started atany of the indicated marks and thereby make it more than unlikely that astudent will get wise to the sequence.

A further object of the present invention is to provide teachingapparatus of this type in which the peripheries of the aforementioneddiscs arebetween their shoulders formed as cams with which theassociated pawls are in spring-urged follower relation, with these carnsbeing designed so that for scoring a registered incorrect answer to aquestion on any displayed card, the pawl associated with the respectivemanipuanswer on any displayed card so that on manipulation of any latedregistration key will in its reciprocatory response he cammed intooperative relation withand actuate the score mechanism, whereas onmanipulation of any registration key for-registration of a correctanswer, the associated pawl will on its reciprocatory response be cammednot only into register with the next shoulder on the associated disc forindexing all discs, but also out of operative relation with the scoremechanism.

It is another object of the present invention to provide teachingapparatus of this type in which its aforementioned response to indexingof the discs in displaying a next card is also used to the same end onmanipulation of the aforementioned index key, by simply providing aratchet wheel which is tumable with the discs and has as many evenlyspaced teeth as there are shoulders on all discs, and an associated pawlwhich on each manipulation of the index key is reciprocated andcooperates with a tooth on the wheel to index the latter and with it alldiscs for a distance of one wheel tooth, with this pawl being on eachreciprocation also brought into operative relation with the scoremechanism to actuate the same for scoring each manipulation of the indexkey the same as a registered incorrect answer to a question on anydisplayed card.

It is a further object of the present invention to provide for teachingapparatus of this type insertable series of cards, of which the cards ofeach series are printed on at least one face and arranged, preferablystacked in a deck and bound, for turnover to bring the printed faces ofsuccessive cards into display, with the correct answers on successivecards to the questions thereon being marked identically and at the samesequence as the registration keys which on their successive manipulationregister correct answers as programmed in the apparatus.

Another object of the present invention is to provide alternativeteaching apparatus of this type which has all the aforementionedfeatures in structure and performance, except that the questions andaccompanying answers are provided, not on printed cards, but asscreen-projected images of questions and indexed one frame onmanipulation of a correct-answer registration key or of the index key.

It is a further object of the present invention to provide teachingapparatus of this type for use with a deck of printed cards which byrings along one edge thereof are bound in looseleaf fashion, with theapparatus having a magazine with an open front facing the registrationand index keys and receiving a deck of cards standing on theirring-bound edges and learning forward, so that the foremost card ondisplay at the front of the magazine will drop out for display of thenext card when a gate thereat is 'on manipulation of a correctanswer keyor of the index key actuated to release the foremost card.

It is another object of the present invention to provide teachingapparatus of this type in which the aforementioned gateis in the form oflugs at the bottom and top of the open magazine front which retaininserted cards in the magazine and which for release of the foremostcards therefrom are reciprocated back and forth along the bottom and topedges of the latter into alternate card-release positions on successivemanipulations of correct-answer registration keys or of the index key,with the cards in the inserted deck having in their bottom and top edgesnotches of which those in successive cards are out of alignment andthose in alternate cards are in alignment, and all notches arecoordinated with the cardretaining lugs so that the notches insuccessive cards are in alignment with these lugs in their alternaterelease positions. With this arrangement, and on further coordinatingthe notches in the cards with the apparatus so that on insertion of anew deck into the magazine with its designated top card foremost thedeck is retained therein by the lugs when the device is then incondition to start a key sequence with a particular key, all the cardsare in correct release coordination with the apparatus in that onmanipulation of the correctanswer registration key or of the index keypursuant to any foremost card in the magazine the lugs will be shiftedto their accompanying answers on successive frames of film which isdropout fromthe magazine.

other card-release position in which they align with the notches in thisforemost card and, hence, clear the latter for its A further object ofthe present invention is to provide teaching apparatus of this type inwhich a deck of cards is inserted in the magazine by simply passing thedeck through the open magazine front, with the top ones of thecard-retaining lugs thereat being to this end yieldable out of the pathof the cards and preferably provided with inclined front faces by whichthey are cammed out of the way of the card deck on its pass into themagazine.

in returning to 0 score indication, and this reset element is providedin the card magazine behind cards therein so as to be normally hiddenand accessible for manipulation only when the magazine isempty. Withthis arrangement, tampering by a student with his or her indicated scoreof incorrect answers is impossible for some students and quite unlikelyfor other students.

It is a further object of the present invention to provide teachingapparatus of this type for alternative use with film as aforementioned,in which the film is indexed one frame by a sprocket which to this endis stepped by having a drive connection with an operating shaft carryingthe aforementioned discs and ratchet wheel, with this drive connectionincluding a friction coupling of which one of the companion membersturns with the operating shaft and the other member is turnable with thefilm sprocket and also with a manual knob which on being turned drivesthe sprocket for bringing the designated first frame of an inserted filminto correct image projecting register with the screen without, however,turning the operating shaft.

Another object of the present invention is to provide teaching apparatusof this type in which, on manipulation of the aforementioned knob forbringing the designated first frame of an inserted film into correctimage projecting register with the screen, the operating shaft ispositively locked against drive by the friction coupling, but this shaftis free to turn and thereby step the film sprocket through the frictioncoupling on manipulation of any correct-answer registration key or ofthe index key.

Further objects and advantages will appear to those skilled in the artfrom the following, considered in conjunction with the accompanyingdrawings.

In the accompanying drawings, in which certain modes of carrying out thepresent invention are shown for illustrative purposes:

' FIG. 1 is a front view of teaching apparatus embodying the presentinvention;

FIG. 2 is a side view of the apparatus;-

FIG. 3 is a fragmentary top view of the apparatus;

FIG. 4 is a fragmentary front view of the apparatus in a differentoperating condition than in FIG. 1;

FIG. 5 is a section through the apparatus taken substantially on theline 5-5 of FIG. 1;

FIG. 6-is a section through the apparatus taken substantially on theline 6-6 of FIG. 2;

FIGS. 7 to 11 are enlarged sections through the apparatus taken on thelines 7-7 to 11-1 1, respectively, of FIG. 6;

FIGS. '12 and 13 are enlarged sections taken on the lines 12-12 and13-13, respectively, of FIG. 6;

FIG. 14 is a fragmentary section through the apparatus taken on the line14-14 of FIG. 6;

FIG. 15 is a chart indicating certain preassigned sequential operabilityof the apparatus;

FIG. 16 is a front view of teaching apparatus embodying the invention ina modified manner; I

FIG. 17 is a section through the modified apparatus taken substantiallyon the line 17-17 of FIG. 16; and

FIG. 18 is a section through the modified apparatus taken substantiallyon the line 18-18 of FIG. I7.

I Referring to the drawings, and more particularly to FIGS. 1

device 24, and answer scoring mechanism 26, which are provided on aframe 28 on a base 30, with the frame 28 being enclosed in a cover 32.

QUESTION-AND-ANSWER DISPLAY UNIT 54 of the frame 28 which also serve asthe sidewalls 44 of the magazine (FIGS. 5 and 6), while the top andbottom walls 46 and 48 are part of a slide 56 having behind the rearmagazine wall 42 a rear plate 58 from which the walls 46 and 48 projectwrwardly and with which they slide for a purpose hereinafter described.The slide 56 is guided for movement back-andforth longitudinally of themagazine, i.e., horizontally in this instance, by headed studs 60 whichextend from the rear magazine wall 42 through slots 62 in the rear plate58 of the latter into the magazine, be out of alignment with the lugs 64to 6 thereof, the reference numeral 20 designates teaching ap- I paratuswhich as: its main operating components has a 'question-and-answerdisplay unit 22, an answer registration.

slide (FIG. 6). The card deck 36 stands edgewise on the bottom wall 48of the magazine 34,-with the foremost card in the deck at the openmagazine front 50 being displayed through a window 63 in the cover 32,and the card deck being retained in the magazine by inwardly projectingtop and bottom lugs 64 and 66 on the top and bottom walls 46 and 48thereof which also are parts oftheslide 56 (FIGS. 1 and 5). For readyinsertion of a card deck 36 into the magazine 34 through the open front50 thereof, the top lugs 64 are yieldable out of the path of the deck onits pass through the open magazine front. To this end, the top magazinewall 46 with the toplugs 64 is hingedly connected with the rear plate 58of the slide 56, by having spaced tongues 68 which extend through hingeslots 70 in the rear plate 58 and are locked therein by being bentagainst the latter (FIGS. 5 and 6), with a leaf spring 72 on the rearplate 58 engaging one of these tongues 68 for nonnally urging the wall46 with its lugs 64 into the position illustrated in FIG. 5 in which thelugs 64 and 66 retain the foremost card of an inserted deck, and with itthe entire deck, in the magazine. Thus, while the top wall 46 with itslugs 64 is hinged to the rear plate 58 of the slide 56, it remainsmovable with the latter in the described guided horizontal direction.The lugs 64 on the hinged top wall 46 are also provided with inclinedforward extensions 74 which by a card deck being passed into themagazine through the open front thereof are cammed out of the way, aswill be readily understood. As already mentioned, the cards standedgewise in the magazine, and by arrangement of the top and bottom lugs64 and 66 the cards also lean forward so that only the top lugs 64prevent their dropout from the magazine (FIG. 5).

The top and bottom lugs 64 and 66 form the gate 40 which retains thecards in the magazine, and for operability of this gate for discharge ofsuccessive cards from the magazine, the top and bottom lugs are providedon the slide 56, as described,

for their movability into opposite card-release positions. However, forcard-release performance of the gate, provisions are also made on thecards themselves to cooperate with the gate in its card-releaseperformance. To this end, the cards are in their top and bottom edgesprovided with top and bottom notches 76 and 78 of which those insuccessive cards are out of aligiment and those in alternate cards arein alignment (FIGS. 1 and 4), with these notches being also coordinatedwith the gate 40 so that the notches in alternate cards are in alignmentwith the lugs 64 and 66 in their opposite cardrelease positions,respectively. Additionally, the notches 76 and 78 in the foremost card.of a deck must, on insertion of the and 66 in the card-release positionwhich theyflthri assume. This latter'condition is demonstrated in FIG. 1in which the notches-76, 78 in the foremost card are out of alignmentwith the lugs 64, 66 in the illustrated card-release position, whereforethese lugs then retain this foremost card in the magazine. However, onshifting the lugs 64, 66 to their other card-release position shown inFIG. 4, these lugs align with the notches 76, 78 to permit dropout ofthe foremost card from the magazine but retain the next card in themagazine until released for dropout on the next shift of the lugs 64, 66to the opposite card-release position (FIG. 1), as will be readilyunderstood. Accordingly, successive foremost cards in the magazine arereleased for dropout therefrom on successive shifts of the lugs 64, 66into their opposite card-release positions until all cards have droppedout.

The cards in the magazine are preferably spring-urged against the lugs64, 66 by the follower plate 80 (FIG. 5) which at 82 has a loose pivotconnection with an arm 84 that extends through a slot 86 in the rearmagazine wall 42 and is held with pivotal freedom therein by a rearflange 88 (FIG. 6). Anchored to lugs 90 and 92 on the rear magazine wall42 and on the rear flange 88 of the arm 84 are the ends of a preloadedspring 94 which urges the follower plate 80 toward the magazine front.

For operating the slide 56 to bring its lugs 64, 66 into the oppositecard-release positions (FIGS. 1 and 4), there is provided an operatingshaft and an operating connection between this shaft and the slide 56.The shaft 100, which is suit'ablyjoumaled in the end walls 54 of theframe 28, carries two cams 102 and 104 (FIGS. 6, 12 and 13 with whichcooperate followers 106 and 108 that are turnable on a fixed shaft 110in the frame 28. The followers 106 and 108 are through links 112 and 114connected with pivoted angle brackets 116 and 118 on the opposite endsof the crossarm 120 of a T-lever 122 which at 124 is pivoted to the rearmagazine wall 42, and which has another arm 126 with a forked end 128receiving a rearwardly projecting pin 130 on the rear plate 58 of theslide 56 (FIGS. 5 and 6). The mounting pin 124 for the T-lever 122projects rearwardly from the rear magazine wall 42 and extends through aclearance slot 132 in the rear plate 58 of the slide 56 so as not tointerfere with the operational movements of the latter. The cams 102 and104 are identical, each having in this instance eight equiangularlyspaced, alternating high and low points 134 and 136, and the two camsare angularly displaced 45 from each other so that a high point 134 ofone cam engages its associated follower when a low point 136 of theother cam engages the associated follower, and vice versa (FIGS. 12 and13). Thus, in the angular position of the cams 102 and 104 shown inFIGS. 12 and .13, the T -Iever 122 is in the angular position shown inFIG. 6 in which the slide 56 is with its'lugs 64,66 in the cardreleaseposition shown in FIG. 4. On next indexing the shaft 100 through 45 inexemplary clockwise direction (FIGS. 12 and 13) the T-lever 122 will berocked to its opposite position to shift the slide 56 with its lugs 64,into the next cardrelease position shown in FIG. 1. The slide 56 is thusshifted back and forth between the two card-release positions onsuccessive indexing steps of the shaft 100 through 45. The provisionsfor successively indexing the shaft 100 also form part of the answerregistration device 24 and will be described later.

Each insertable card deck is preferably bound not only to hold the cardsthereof in their prearranged succession but also to avoid the loss ofany card. To this end, the cards 38 in the exemplary deck 36 areprovided with aligned holes 140 and 142 along the edge on which theystand in the magazine, i.e., their bottom edge, and rings 144 and 146extend through the respective aligned holes 140 and 142 to bind thecards in looseleaf fashion. The rings 144 and 146 in the inserted carddeck 36 freely depend therefrom and act as hinges to guide releasedcards into orderly superposition on a ledge 148 on the cover 32 (FIG.5), with the bottom wall 48 of the slide 56,

being also the bottom wall of the magazine, being interrupted I pawl Theanswer registration device 24 is adapted to register the answer astudent selects as the correct one from a number of given answers to aproblem question on each displayed card in an inserted deck in themagazine, of which the given answers to each question include only onecorrect one. Thus, the correct answer to the question on the exemplarydisplayed card in FIGSpI and 4 is PAIN and the other given answers areobviously wrong, wherefore a student knowing the correct answer willregister PAIN as his or her chosen answer. All question" cards in thedeck, i.e., cards other than possible explanatory or introductory cards,present different problem questions with the same number of answersthereto, in this instance four, of which only one answer in eachnumberof answers is the correct one. All of these question cards are ofthe same general forma as the exemplary displayed card in FIGS. 1 and 4in the relative location of the answers to each other and to theassociated problem question, i.e., the answers on successive cards arein this instance provided below the respective questions and arepreferably arranged in superposed rows so that the answers on successivedisplayed cards appear in the same location and order from left to rightas the answers shown in FIGS. 1 and 4. Further, the answers on each cardare provided with individually distinguishing marks, and thedistinguishing marks on the answers on all cards are the same, with likemarks being preferably applied to the answers on all cards which are ofthe same order in the respective rows of answers. Thus, with theexemplary distinguishing marks of the answers on the displayed card inFIG. 1 being a triangle" mark, a square" mark, a cross mark, and acircle mark for the four answers, the answers on all cards are providedwith these same marks, with the leftmost questions on all cardspreferably bearing the same triangle mark (FIG. I) and the otherquestions bearing the other marks in the same order in which they appearin FIG. 1.

The answer registration device includes as many individuallymanipulatable keys 160 as there are answers to the question on eachcard, i.e., four in the given example. These keys 160 are provided onlevers 162 which are tumable on a fured shaft 164 in the frame 28 (FIG.5), with these levers I62 extending through slots 166 in the front wallll68 of the cover 32 and carrying in front of the latter the respectivekeys 160,

and these same levers also extending through slots 170 in a rear channel172 in the frame 28. The rear end of each of these levers 162 is at 174pivotally connected with a pawl 176 which cooperates with a disc 173 onthe shaft 100 (FIGS. 5, 6 and 8 to 11) this being the shaft which alsocarries the described earns 102 and 104 for operating the slide 56. Thelevers E62 are, by springs 182 acting on their associated pawls 176,normally urged into the position shown in FIG. 5 in which they bearagainst the bottom walls 180 of the slots 170 in the channel 172 throughwhich they extend, so that the keys 160 are normally in the raisedposition shown in FIGS. 1,4 and 5, and may be individually depressed foroperation of their associated pawls 176.

Each of the discs 178 on the shaft 100 has at least one, and preferablymore than one, peripheral tooth 184 each with a shoulder 186, of whichthe shoulders of the teeth of all discs are equiangularly spaced. In thepresent example, there are four of these discs 178, one for eachassociated key 160 and 176, and each disc has an exemplary number of twoshoulders. Each pawl 176 is provided at its upper end with a hookformation 188 with which the pawl is by the associated spring 182 urgedinto following engagement with the periphery ofthe associated disc I78(FIGS. 6 and 9).

Like discs 178 in FIGS. 6 and 8 to II are identified as discs 178a to178d and their associated pawls 176 are similarly identified as pawls176a to 176d, and the keys associated with the respective pawls 176a to176d and respective discs 178a guishing marks as the answers on eachdisplayed card,

whereby each key 160 is by its mark associated with the answer of thesame mark on all displayed cards. The different marks on the keyspreferably also follow each other from the left end key 160d to theright end key 160a in the same order in which the same marks follow eachother on the answers on the displayed card (FIGS. 3 and 4), therebyfacilitating visual association of the answers with the similarly markedkeys.

As already mentioned, the shaft with the earns 1.02, 104 and the discs178a to 178d thereon is to be indexed one step for each operation of theslide 56 with its lugs 64, 66 to release the foremost card from themagazine front and display the next card thereat. Each such indexing ofthe shaft 100 is achieved on depression of a certain one among the keysthrough cooperation of the associated pawl 176 and disc 178, withsuccessive indexing steps of this shaft 100 being achieved on depressionof successive keys in a preassigned sequence to be described. Innondepressed condition of the keys 160 all pawls 176 are at the level ofthe pawl 176b shown in full lines in FIG. 9, and each pawl is ondepression of its associated key raised to the level of the key 176i; inits dotted line position in FIG. 9. Further, the discs 178 are socoordinated with their associated pawls that only one shoulder 186 amongall shoulders on the discs is in an operating position for indexingcooperation with the associated pawl on depression of the associatedkey, and this shoulder is in this instance the shoulder 186 on the discl78b in the angular operating position P in FIG. 9. Thus, on depressingthe associated -key 160b, pawl I76b will be raised to its dotted lineposition (FIG. 9) in which the associated spring 182 swings this pawlwith its hook formation 188 over the shoulder 186', whereby on releaseof the depressed key 160!) and ensuing spring-return of the pawl I76b toits lower full-line position, disc 178b, and with it the shaft 100 andall discs thereon, will be indexed one step, clockwise as viewed inFIGS. 5 and 8 to 11, with the indexing step being equal to the angulardistance between successive shoulders on the discs, i.e., 45 inconformity with the described 45 stepping of the cams 102 and 104 forrelease of each forward card from the magazine from and display of thenext card thereat. In thus indexing the disc 17812 at its shoulder 186',the latter will on spring-return of the associated pawl I76b to itslower, full-line, position (FIG. 9) arrive at an angular position likethat ofthe shoulder 186" on the disc 178a in FIG. 8, and the shoulderson all discs will advance clockwise one step of 45, with a next shoulder186 then also arriving at the angular operating position P, this beingin the present instance the shoulder 186' on the disc i'lfid (FIG. 11).

It follows from the proceeding that in the particular angular restposition between steps of the shaft 1th) and discs 178 thereon as shownin FIGS. 8 to 1l,'only depression of the key 16Gb and ensuingcooperation between the associated pawl 176b and disc 178b will bringabout an index step of the shaft and discs, and that depression of anyother key will not index the same. Also, while under these circumstancesdepression of the key 16% will result in discharge of the foremost cardfrom the magazine, this being the one shown in FIGS. 1 and 4, anddisplay of the next card, depression of this particular key 16% alsodenotes that the student selecting this key for depression therebyregisters among the given answers to the question on the displayed cardthe one answer which he or she believes to be the right one. Thus, withthe student selecting among the given answers to the question on thethen displayed card (FIG. 1) the PAIN answer as the correct one, thestudent proceeded to register his or her selected answer by depressingthe key which bears the same mark as the selected answer on the card,with this mark being in this instance the cross mark (FIGS. 3 and 4).Accordingly, since depression of the key I60!) in this instance doesbring about discharge of the displayed card from the magazine front anddisplay. of the next card thereat, this also confirms to the studentthat the answer he or she selected from the given answers as the correctone and so registered the same by depressing this particular key, wasindeed the cor rect answer.

As already pointedout, depression of the key 160!) will cause indexingof the shaft 100 and discs 178 thereon from the position in FIGS. 8 to11 through one step at the end of which the shoulder 186" on disc 178dwill be in the angular operating position P. Accordingly, with theshoulder 186" on the disc 178d being then in this operating position P,only depression of the associated key 160d will bring about the nextindexing step of the shaft 100 and discs [78 thereon, and with this key160d bearing the exemplary triangle mark (FIG. 3), the one answer amongthe four given answers to the question on the then displayed card whichbears the same triangle mark must be the correct answer. Of course, themarks of the answers on the cards in the inserted deck are so arrangedthat this will be the case.

It will now be understood that the shaft 100 with the discs 178 and cams102, 104 will be indexed successively on successive depressions of thekeys 160 in a certain sequence which is the same as the programmedsequence of the respective discs 178 whose shoulders 186 follow eachother into the angular operating position P. Thus, the order in whichthe shoulders 186 on the discs 178 follow each other into the operatingposition P is indicated bysuccessive numbers l to 8 in FIGS. 8 to 11,with the shoulder 186 in the operating position P (FIG. 9) being in thisinstance marked as the number l shoulder. Accordingly, the seqt ence ofthe discs whose shoulders follow each other into the operating positionP is disc l78bdisc l78d--disc 178b- -disc 178cdisc 178a--disc 178c, discl78ddisc 178a, wherefore the sequence of the keys which on successivedepression cause successive indexing steps of the shaft 100 and discsand earns thereon, being as the sequence of their associated discs, iskey 160b-key 160dkey 160b-key 160c-key 160akey 160c-key 160d- -key 160a.This key sequence, which starts with the key 160b, is graphicallyillustrated in FIG. as the sequence A, with the order of the keys inthis sequence being noted by the dots below the respective indicated,marked keys 160a to 160d. Thus, assuming that the exemplary displayedcard in FIG. I is the topmost card of an inserted deck, successivedepressions of the keys in this and each recurring sequence, startingwith the key l60b, will bring about the discharge of successive cardsfrom the magazine front and display of the next cards thereat until allcards are discharged, provided the marks on the given correct answers toquestions on successive displayed cards are arranged, as they must be,to follow each other as the same marks on the keys being successivelydepressed in the sequence.

Assuming that the marked answers on the cards of any insertable deck arecoordinated to require for correct-answer registration depression of thekeys in the sequence A starting with key l60b, the discs 178 on theshaft 100 must at insertion of any card deck be in the correspondingangular sequencestart position in FIGS. 8 to 11. Of course, the numberof cards in any deck will be selected so that on discharge of the lastcard from the magazine the discs 178 will be in this sequencestartposition. However, to afford visual indication of the sequence-startposition of the discs and also manual turning of the discs into theirsequence-start position if need be, the shaft 100 carries on the outsideof the cover 32 a knob 200 (FIGS. 1, 2 and 6) having a marking, in thisinstance a line identified by the character A, and there is provided onthe cover 32 a fixed pointer 202 (FIG. 2), with these being coordinatedso that the discs 178 are in their sequence-start position when the Aline on the knob is in alignment with the pointer 202. Should the discs178 be returned from any other angular position to their sequence-startposition, the knob 200 may be turned, clockwise as in FIG. 2, until theA line aligns with the pointer 202. Manual turning of theknob 200 inthis fashion will result in like clockwise turning of the discs 178(FIGS. 8 to 11), with the pawls 176 simply overriding the discshoulglers 186, as will be readily understood.

Preferably, the knob 200 has as many equiangularly spaced line marks asthere are shoulders on the discs, with these line marks being identifiedby the successive characters A to H, and successive ones of these linemarks denoting the order of the shoulders in the sequence in which theyfollow each other into the angular operating position P. With-thisarrangement, the sequence of successive depressions of the keys 160 forsuccessive correct-answer registrations and ensuing discharge ofsuccessive cards from and display of the next cards at the magazinefront, may be made to start with the denoted order of any shoulder, bysimply turning the knob 200 to bring the corresponding line mark thereoninto alignment with the pointer 202. There are thus available as manysequence-start positions of the discsl'78 as there are shoulders 186 onthe discs. The sequences of successive correct-answer depressions of thekeys corresponding to the different sequence-start positions of thediscs are also indicated in FIG. 15 by the groups of dots identified bythe characters A to H. By changing the sequence-start positions of thediscs for different decks of cards, the chances that a student may getwise to the key sequence in any given case are virtually nil. Further,it is exceedingly simple to coordinate the cards of any deck with thekey sequence pursuant to any sequence-start position of the discs, byproviding the given correct answer to the question on the first cardwith the same mark as that on the key with which to start the keysequence for correct-answer registrations.

To permit the use with the teaching apparatus of card decks having amongquestion cards also other cards requiring no student answer, such as anintroductory top card or one or more intermediate cards bearinginstructions or explanations relative to a succeeding question card orcards, there is provided, in addition to the answer registration" keys160, another key 204, i.e., an index key, which is operatively connectedwith the shaft and manipulatable to index the latter and the discs 178and cams 102, I04 thereon through one regular step. This index key 204,which is in this instance marked NEXT (FIG. 3), is carried by a lever206 (FIG. 6) which is tumable on the shaft 164 the same as the levers162 (FIG. 5), and at its rear end pivotally carries at 208 a pawl 210(FIGS. 5 and 6) which cooperates with a ratchet wheel 212 having as manyperipheral teeth 214 as there are shoulders on the discs 178, i.e.,eight in this instance. The pawl 210 has at its upper end a hookformation 216 with which it is normally urged against the periphery ofthe ratchet wheel 212 by a pawlretum spring 218 which normally urges thepawl into the retracted position in FIG. 5 in which the index key 204 isin its raised position (FIGS. 1, 2 and 4) in which it is depressible.downwardly for its manipulation. In thus depressing the index key 204,the pawl 210 is raised to a point where the same is by its return spring218 rocked with its hook formation 216 into register with the shoulder220 of the nearest tooth ('FIG. 5), whereby on release of the depressedindex key 204 the pawl 210 is spring-returned to its inoperativeposition in FIG. 5 and indexes the ratchet wheel 212 and with it theshaft 100 and discs 178 and earns 102, 104 thereon, through one regularstep. In consequence, the foremost displayed card at the magazine frontwill be discharged and the next card displayed thereat withoutmanipulation of any registration key 160. Of course, since the ratchetwheel 212 has as many teeth 214 as there are shoulders on the discs 178,the foremost card at the magazine front will be discharged and the nextcard displayed thereat on each depression of the index key 204. Also,since each depression of the index key 204 results in an indexing stepof the shaft 100 and discs 178 thereon, it stands to reason that thishas to-be taken into account in providing the given correct answers onsuccessive question cards with the correct distinguishing marks so thaton their registration by a student with registration keys of the samemarks the registered answers indeed conform to the given correctanswers.

1 l ANSWER SCORING MECHANISM Provisions are also made to score thenumber of registered incorrect student answers to the questions on thecards of an inserted deck. To this end, there is freely tumable on theshaft 100 a ratchet disc 230 (FIGS. 6 and 14) with the teeth 232 ofwhich cooperates an indexing pawl 234 that is at 236 pivotally carriedby one of the end legs 238 of a U-shapcd bar 240. This bar 240 is withits legs 238 freely tumable on the shaft 100,

' and is normally urged by a spring 242 against a stop pin 244 on one ofthe end walls 54 of the frame 28 (FIGS. 5, 6 and i4), while the pawl 234is by a spring 246 held against the ratchet disc 230. Also cooperatingwith the teeth of the ratchet disc 230 is a spring-urged holding pawl248 which at 250 is pivotally mounted on one of the end walls 54 of theframe 28. Secured with one end to, and wound on, the hub 252 of theratchet disc 230 is a flexible cable 254 the other end of which isanchored to one end of a tensioned spring 256 which is with its otherend anchored to a lug 258 on the frame 28 (FIG. 6) with this springnormally urging the ratchet disc 230 clockwise into the score startposition in FIG. 14 in which a peripheral lug 260 on the disc bearsagainst the indexing pawl 234. The ratchet disc 230 is in its outer faceprovided with equiangu larly spaced successive score numbers startingwith of which the 0 number registers with a window 262 in the cover 32when the ratchet disc is in its score start position,

Each of the pawls 176 associated with the respective registration keys160 has near its top a rear leg 264 with a shoulder 266 (FIG. 9). Forscoring each registered incorrect student answer, the shoulder 266 onthe pawl 176 which responds in rising to the depression of the wrongselected registration key 160 will engage the bar 240 and rock the sameagainst its spring 242 clockwise as viewed in FIG. 14, sufficiently tobring the indexing pawl 234 into register with the next tooth of theratchet disc 230, whereby on release of the depressed registration key160 and ensuing spring-return of the bar 240 against the stop pin 244,the also returning indexing pawl 234 will take the ratchet disc 230along for one tooth, i.e., one indexing step, in counterclockwisedirection (FIG. 14) to bring the next score number on this disc intoregister with the window 262. Conversely, on registering any correctstudent answer, as on depressing the key 160b in the exemplary angularposition of the discs 178 in FIGS. 8 to 11, the ratchet disc 230 is notindexed, because on the ensuing rise of the associated pawl 176b fromits full-line position to its dotted line position (FIG. 9), the flank268 of the tooth 184 whose shoulder 186' is then in the operatingposition P serves to cam this pawl with its shoulder 266 out ofoperative relation with the bar 240 as shown in the momentarydot-and-dash line position of this pawl in FIG. 9. On the other hand,and still with reference to the angular position of the discs 178 inFIGS 8 to 11, on depression of any registration key 160 other than key160b, the associated pawl 176 will on its ensuing rise be in followerrelation with a circular part of the periphery of the associated disc178 and thereby guided with its shoulder 266 into operative engagementwith the bar 240 to index the ratchet disc 230 one step and therebyscore a registered incorrect student answer, as will be readilyunderstood.

To prevent a student from tampering with the score of registeredincorrect answers at least until all cards of an inserted deck have beendealt with by the student and discharged from the magazine, the holdingpawl 248 extends through an openmg 270 in one of the sidewalls 44 of themagazine and has in the latter behind any inserted card deck therein ahandle end 272 (FIGS. 1, and 14) which only in the absence of any cardin the magazine is accessible through the open magazine front formanipulation to release this pawl 248 from the ratchet disc 230 andpermit spring-retum of the latter to its score start position (FIG. 14).

Provisions are also made to score each depression of the index key 204as an incorrect student answer. To this end, the associated pawl 210 hasnear its top a rear leg 274 with a shoulder 276 (FIG. 5), with thisshoulder being led into operating engagement with the bar 240 on eachrise of this pawl into register with the next tooth shoulder 220 on theratchet wheel 212 pursuant to each depression of the index key 204.Thus, a student will not evade an incorrect answer score if he or shedoes not know which one of the given answers to a question on anydisplayed card is the correct one and, in consequence, manipulates theindex key 204 rather than any of the registration keys 160. On the otherhand, it is a simple matter to arrive at the true score of registeredincorrect student answers to the questions in a deck ofv cards havingbesides question cards also introductory or explanatory cards requiringno student answer, by simply deducting from the indicated score thedesignated number of such introductory or explanatory cards in the deck.

The presentteaching apparatus, while highly useful for individualstudent quizzing with insertable card decks, is also useful forsimultaneously quizzing the students in a class by providing eachstudent with a teaching apparatus without a deck of cards, anddisplaying by or under the control of a teacher or supervisor successivequestions and given marked answers thereto of sufficiently large size tobe readable by all students, with the students registering theirselected answers to the questions, and the apparatus of each studentindicating his or her incorrect-answer score at the end of a class quiz.

While in the described teaching apparatus the problem questions andanswers thereto are given on cards of insertable decks, FIGS. 16 to 18show a modified teaching apparatus 20a in which the problem questionsand answers thereto are provided on successive frames f of an insertablefilm F, and these questions and answers are for their display projectedon a screen 280 (FIG. 16). To this end, the modified apparatus 20a has alight source in the form of an electric bulb 282, a lens system 284, afilm guide 286 with a window 288, a reflector 290, a film feed sprocket292, and the screen 280 which is provided in a front opening 294 in acasing 296. Film F is insertable in the guide 286 at the open topthereof (FIG. 16), and is near the lower end of this guide 286 led overthe feed sprocket 292 and directed into a channel 298 that leads to acollection chamber 300 which is open at the top for removal of a spentfilm (FIG. 17). The film sprocket 292, which is car.- ried by a suitablyjoumaled shaft 302, has a drive connection with the shaft a carrying thediscs 1780' to 178d and the ratchet wheel 212a, so that the sprocket 292is turned to feed the film F the distance of one frame f in thedirection of the arrow 304 (FIG. l8) on each indexing step of the shaft100a pursuant to depression of a given one of the registration keys1600' to d or of the index key 2040. The drive connection between thefilm sprocket 292 and shaft 100a provides, in this instance, a pulley306 on the sprocket shaft 302, a pair of pulleys 308 freely tumable on afixed shaft 310, a pulley 312 on one of the companion members 314 of afriction coupling 316 the other member 318 of which is carried by theshaft 100a, and a belt 320 passed over the pulleys 306, 308 and 312 inthe manner shown in FIGS. 17 and 18. The coupling member- 314 is carriedby a suitably joumaled shaft 322, and the coupling members 314, 318' arenormally held in frictional driving engagement with each other byspring-urged bolts 324 which act on a strap 326 that urges couplingmember 318 against its companion member 314. The shaft 322 extends tothe outside of the casing 296 and carries'a hand wheel 328 with which toturn the coupling member 314 relative to its companion member 318 inoperating the sprocket 292 to feed the leading end of inserted film Finto the channel 298 and bring the first film frame I into register withthe window 288 in the film guide 286 and, hence, also with the screen280. To prevent rotation of the shaft 1000 on the manual drive of thefilm sprocket 292 by the knob 328 for film registration as described,the shaft 10011 is locked against rotation. To this end, the shaft 100acarries, in addition to the discs 178a to 178d and ratchet wheel 212a, alock disc 330 having as many equiangularly spaced peripheral grooves 332as there are shoulders on the discs 178a to 178d, and a bar 334 having atooth 336 and opposite end flanges 338 with which the bar is pivotallymounted I3 on the fixed shaft 1640. The bar 334 spans the levers 162aand 206a associated-with the registration keys 160a to 160d' and withthe index key 2044 (FIG. 17), and this bar is by a spring 340 normallyurged with its tooth 336 into locking register with any aligned'groove332 in the lock disc 330 (FIG. 18);

However, while the bar 334 thus locks the shaft 100a against rotation onthe manual drive of the film sprocket 292 by the knob 328, this bar isretracted from locking relation with the lock disc 330 on depression ofany of the keys 160a to 160d or 204a into the dot-and-dash line positionin FIG. 18 in the course of which its associated lever 1620 or 206a ismoved into the indicated dot-and-dash line position to engage the bottomedge of the bar and turn the latter into the retracted dot-and-dash lineposition, all as shown in FIG. 18. Accordingly, the bar 334 neverinterferes with the orderly indexing of the shaft 100a on depression ofthe respective keys 160a to 160d for correct-answer registrations or oneach depression of the index key The present apparatus 200 thus performsin every respect in the same manner as the earlier described apparatus20 of FIGS. 1 to 6, except that successive problem questions and thegiven answers thereto are projected onto a screen rather than by displayof successive cards on which the answers and questions are printed.Further, in

the present teaching apparatus, the distinguishing marks on circlemarks. Of course,the same holds for the teaching device 20 in FIGS. 1 to6 on aligning the registration keys 160a to 160d with the answers to thequestion on each displayed card. Cooperating with either teachingapparatus of FIGS. I to 6 or FIGS. 16 to 18 may be an audio device inthe form of a battery-powered tape reproducer 350 (FIG. 7) holding areplaceable tape with recorded successive narrations relative tosuccessive displayed problem questions, with the reproducer 350 startingand proceeding with the reproduction of each recorded narration onmomentary closure of a normally open switch 352, and self-stopping atthe end of each narration. For cooperation of such a reproducer with theteaching apparatus of FIG. 1 to 6, the switch- 352 is coorwith theratchet wheel 212 (FIG. 7) so as to be momentarily closed by a tooth 214thereof near the end of each indexing step of the shaft 100. Such areproducer may also cooperate with the teaching device 20a of FIGS. 16to 18 on similarly coordinating the switch 352 with the ratchet wheeland means operating said tifiiii on each indexing step of said discs todisplay a next element, whereby said'u'nit is-operated only onmanipulation of any key which is in the order. of the same key in asequence of successive manipulations of said keys starting and recurringwith a given key, with said sequence being as the programmed, sequenceof the discs whose shoulders follow each other into said operatingposition. I

2. Teaching apparatus as in claim '1, said keys is more than two.

3. Teaching apparatus as in claim I, in which said shoulders are of alarger number than said keys.

4. Teaching apparatus as in claim 1, in which said pawls are inspring-urged follower relation with said discs and override saidshoulders on turning said discs in said one direction relative to saidpawls, and there is further provided a fixed pointer, and a manual knobtumable with said discs and provided with a marking, with said knobbeing tumable in said one direction for turning said discs in the samedirection to bring said marking into alignment with said pointer, andsaid marking and pointer being coordinated so that on their alignmentsaid keys are at the start of said manipulation sequence.

5. Teaching apparatus as in claim 4, in which said knob has as manyequiangularly spacedv different markings as there are shoulders on saiddiscs, with successive ones of said markings being associated with saidshoulders in the order in which they in which the number of follow eachother into said operating position, and said markings and pointer beingcoordinated so that on alignment of any marking with said pointer theassociated shoulder is in said angular operating position, whereby a keymanipulation sequence may be started on alignment of any of saidmarkings with said pointer.

6. Teaching apparatus as in claim 1, which further provides mechanismoperable to score each registered incorrect student answer, and meansfor operating said mechanism providing cam formations on said discs andincluding said pawls, with each pawl being on manipulation of itsassociated key diverted by the cam formation on the associated disc intooperating relationship with said mechanism if the shoulder on theassociated disc is out of said operating position.

7. Teaching apparatus as in claim 6, in which said mechanism provides atumable ratchet disc with equiangularly spaced successive numbersstarting with zero, a fixed pointer, and another pawl reciprocated byany of said diverted pawlsto index said ratchet disc in onedirection foraligning 2120. Further, the latter teaching apparatus may also beprovided with a compartment 326 for reception of a reproducer 350.

lclaim: Y

1. Teaching apparatus, comprising a unit for insertion therein of aseries of elements and operable to display succes sive elements, one foreach operation, of an inserted series of which each element presents aproblemquestion and a given number of answers thereto including onecorrect one;- and a student-answer registering device providingindividually manipulatable keys of said given number, coaxial discsaswith said keys, respectively, and tumable in unison, of which each hasat least one shoulder and the shoulders of all discs are equiangularlyspaced, with one shoulder being in a predetermined angular operatingposition, pawls associated with said keys, respectively, of which eachpawl is on manipulation of the associated key moved to be in registerwith the shoulder on the associated disc if said shoulder is in saidangular operating position, with any pawl registering with the shoulderon the associated disc indexing'all discs through one step equal to thedistance between successive shoulders, key.

the next higher one of said numbers with said pointer.

8. Teaching apparatus as in claim 7, in which said ratchet discisnormally urged in a return direction opposite to said one direction, andthere is further provided afixed stop limiting return of said ratchetdisc to a start position in which said zero number aligns with saidpointer, a spring-urged holding pawl preventing return of said ratchetdisc from any indexed position to said start position, and manual meansfor releasing said holding pawl from, said ratchet disc for return ofthe latter to said start position. I

9. Teaching apparatus as in claim 8, in which said unit includes amagazine having an open front and being'otherwise closed for removablereception of an element series in the form of stacked printed cards ofwhich each foremost card is displayed at said magazine front, and saidmanual pawl releas-.

- ing means is provided in said magan'ne rearwardly spaced from saidopen front thereof so that access thereto is blocked by cards in saidmagazine.

10. Teaching apparatus as in claim 1, in which said keys areregistration keys, and there is furtherprovided amanipulatable indexkey, a wheel tumable with said discs and having equiangularly spacedteeth equal in number to said shoulders, and another pawl moved on eachmanipulation of said index key to register with a tooth on said wheeland index the latter and all discs in said one direction through one ofsaid steps for operation of said unit without manipulation of aregistration associated the registration keys are'fi-rst pawls, andthereis further providedmechanism operable to score each registeredincorrect-student answer, first means for operating said mechanismproviding cam formations on said discs and including said first pawls,with each of said first pawls being on manipulation of its associatedregistration key diverted by the cam fomiation on the associated discinto operating relation with said mechanism if the shoulder on theassociated disc is out of said operating position, and other means foroperating said mechanism providing cam portions on said wheel andincluding said other pawl, with said other pawl being on eachmanipulation of said index key also moved by a cam portion on said wheelinto operating relation with said mechanism, whereby each manipulationof said index key is also scored as an incorrect student answer.

I 12. Teaching apparatus as in claim 1, in which said unit provides anopen-front magazine for removable reception of an element series in thetom of stacked printed cards with 0pposite edges and standing on oneedge, with the foremost card being displayed at the magazine front, andsaid cards having in opposite edges notches of which the notches insuccessive cards are out of alignment and the notches in alternate cardsare in alignment, a member movable into opposite positions and having atand within the confines of the open magazine front lugs retaining eachforward card in, and permitting removal of the same from, the magazinefront when in said opposite positions of said member said lugs are outof alignment and in alignment, respectively, with said notches in saidforemost card, and means operable to move said member from either ofsaid opposite positions to the other of said opposite positions.

13. Teaching apparatus as in claim 12, in which said lugs are arrangedin pairs at the top and bottom, respectively, of the magazine front tocooperate with the notches at the top and bottom of cards standing withtheir bottom edges in the magazine.

14. Teaching apparatus as in claim 13, in which the lugs of one of saidpairs are yieldable out of the confines of the open 16' magazine frontand have inclined front surfaces, whereby stacked cards are insertableinto the magazine through the open front thereof by camming the lugs ofsaid one pair at said inclined surfacesout of the confines of the openmagazine front.

15. Teaching apparatus as in claim 1, in which said unit pro vides afilm projector for removable reception of film with a series ofsuccessive answer and question frames, a screen on which to project theanswer and question images from successive frames, a tumable film feedsprocket, and a drive connection between said discs and sprocket foroperating the latter to index film one frame on' each indexing step ofsaid discs.

16. Teaching apparatus as in claim 15, in which said drive connectionincludes a friction coupling having companion members of which onemember turns with said discs andthe other member turns with saidsprocket, and there is further provided a knob turning with said othermember and tumable to drive said sprocket relative to said discs forbringing film into register with said screen. 7

17. Teaching apparatus as in' claim 16, which further provides meansnormally locking said disc's against rotation and operable by any ofsaid keys on its manipulation to release said discs for one of saidindexing steps.

l8. Teachi ng apparatus as in claim 17, in which said locking meansprovides a disc part'tuming with said discs and having in its peripheryequiangularly spaced grooves equal to the number of said shoulders, anda key part tumable about-a fixed pivot into and from locking registerwith any aligned one of said grooves and normally spring-urged intolocking register therewith, with said key part having a shoulder engagedby any of said keys on its manipulation for turning said key part fromlocking register with any of said grooves;

19. Teaching apparatus as in claim 1, having provisions for visuallyassociating said keys with the respective answers to the auestion oneach displayed element. 2 Teaching apparatus as in claim 19, In whichsaid provi-

1. Teaching apparatus, comprising a unit for insertion therein of aseries of elements and operable to display successive elements, one foreach operation, of an inserted series of which each element presents aproblem question and a given number of answers thereto including onecorrect one; and a student-answer registering device providingindividually manipulatable keys of said given number, coaxial discsassociated with said keys, respectively, and turnable in unison, ofwhich each disc has at least one shoulder and the shoulders of all discsare equiangularly spaced, with one shoulder being in a predeterminedangular operating position, pawls associated with said keys,respectively, of which each pawl is on manipulation of the associatedkey moved to be in register with the shoulder on the associated disc ifsaid shoulder is in said angular operating position, with any pawlregistering with the shoulder on the associated disc indexing all discsthrough one step equal to the distance between successive shoulders, andmeans operating said unit on each indexing step of said discs to displaya next element, whereby said unit is operated only on manipulation ofany key which is in the order of the same key in a sequence ofsuccessive manipulations of said keys starting and recurring with agiven key, with said sequence being as the programmed sequence of thediscs whose shoulders follow each other into said operating position. 2.Teaching apparatus as in claim 1, in which the number of said keys ismore than two.
 3. Teaching apparatus as in claim 1, in which saidshoulders are of a larger number than said keys.
 4. Teaching apparatusas in claim 1, in which said pawls are in spring-urged follower relationwith said discs and override said shoulders on turning said discs insaid one direction relative to said pawls, and there is further provideda fixed pointer, and a manual knob turnable with said discs and providedwith a marking, with said knob being turnable in said one direction forturning said discs in the same direction to bring said marking intoalignment with said pointer, and said marking and pointer beingcoordinated so that on their alignment said keys are at the start ofsaid manipulation sequence.
 5. Teaching apparatus as in claim 4, inwhich said knob has as many equiangularly spaced different markings asthere are shoulders on said discs, with successive ones of said markingsbeing associated with said shoulders in the order in which they followeach other into said operating position, and said markings and pointerbeing coordinated so that on alignment of any marking with said pointerthe associated shoulder is in said angular operating position, whereby akey manipulation sequence may be started on alignment of any of saidmarkings with said pointer.
 6. Teaching apparatus as in claim 1, whichfurther provides mechanism operable to score each registered incorrectstudent answer, and means for operating said mechanism providing camformations on said discs and including said pawls, with each pawl beingon manipulation of its associated key diverted by the cam formation onthe associated disc into operating relationship with said mechanism ifthe shoulder on the associated disc is out of said operating position.7. Teaching apparatus as in claim 6, in which said mechanism provides aturnable ratchet disc with equiangularly spaced successive numbersstarting with zero, a fixed pointer, and another pawl reciprocated byany of said diverted pawls to index said ratchet disc in one directionfor aligning the next higher one of said numbers with said pointer. 8.Teaching apparatus as in claim 7, in which said ratchet disc is normallyurged in a return direction opposite to said one direction, and there isfurther provided a fixed stop limiting return of said ratchet disc to astart position in which said zero number aligns with said pointer, aspring-urged holding pawl preventing return of said ratchet disc fromany indexed position to said start position, and manual means forreleasing said holding pawl from said ratchet disc for return of thelatter to said start position.
 9. Teaching apparatus as in claim 8, inwhich said unit includes a magazine having an open front and beingotherwise closed for removable reception of an element series in theform of stacked printed cards of which each foremost card is displayedat said magazine front, and said manual pawl releasing means is providedin said magazine rearwardly spaced from said open front thereof so thataccess thereto is blocked by cards in said magazine.
 10. Teachingapparatus as in claim 1, in which said keys are registration keys, andthere is further provided a manipulatable index key, a wheel turnablewith said discs and having equiangularly spaced teeth equal in number tosaid shoulders, and another pawl moved on each manipulation of saidindex key to register with a tooth on said wheel and index the latterand all discs in said one direction through one of said steps foroperation of said unit without manipulation of a registration key. 11.Teaching apparatus as in claim 10, in which the pawls associated withthe registration keys are first pawls, and there is further providedmechanism operable to score each registered incorrect student answer,first means for operating said mechanism providing cam formations onsaid discs and including said first pawls, with each of said first pawlsbeing on manipulation of its associated registration key diverted by thecam formation on the associated disc into operating relation with saidmechanism if the shoulder on the associated disc is out of saidoperating position, and other means for operating said mechanismproviding cam portions on said wheel and including said other pawl, withsaid other pawl being on each manipulation of said index key also movedby a cam portion on said wheel into operating relation with saidmechanism, whereby each manipulation of said index key is also scored asan incorrect student answer.
 12. Teaching apparatus as in claim 1, inwhich said unit provides an open-front magazine for removable receptionof an element series in the form of stacked printed cards with oppositeedges and standing on one edge, with the foremost card being displayedat the magazine front, and said cards having in opposite edges notchesof which the notches in successive cards are out of alignment and thenotches in alternate cards are in alignment, a member movable intoopposite positions and having at and within the confines of the openmagazine front lugs retaining each forward card in, and permittingremoval of the same from, the magazine front when in said oppositepositions of said member said lugs are out of alignment and inalignment, respectively, with said notches in said foremost card, andmeans operable to move said member from either of said oppositepositions to the other of said opposite positions.
 13. Teachingapparatus as in claim 12, in which said lugs are arranged in pairs atthe top and bottom, respectively, of the magazine front to cooperatewith the notches at the top and bottom of cards standing with theirbottom edges in the magazine.
 14. Teaching apparatus as in claim 13, inwhich the lugs of one of said pairs are yieldable out of the confines ofthe open magazine front and have inclined front surfaces, wherebystacked cards are insertable into the magazine through the open frontthereof by camming the lugs of said one pair at said inclined surfacesout of the confines of the open magazine front.
 15. Teaching apparatusas in claim 1, in which said unit provides a film projector forremovable reception of film with a series of successive answer andquestion frames, a screen on which to project the answer and questionimages from successive frames, a turnable film feed sprocket, and adrive connection between said discs and sprocket for operating thelatter to index film one frame on each indexing step of said discs. 16.Teaching apparatus as in claim 15, in which said drive connectionincludes a friction coupling having companion members of which onemember turns with said discs and the other member turns with saidsprocket, and there is further provided a knob turning with said othermember and turnable to drive said sprocket relative to said discs forbringing film into register with said screen.
 17. Teaching apparatus asin claim 16, which further provides means normally locking said discsagainst rotation and operable by any of said keys on its manipulation torelease said discs for one of said indexing steps.
 18. Teachingapparatus as in claim 17, in which said locking means provides a discpart turning with said discs and having in its periphery equiangularlyspaced grooves equal to the number of said shoulders, and a key partturnable about a fixed pivot into and from locking register with anyaligned one of said grooves and normally spring-urged into lockingregister therewith, with said key part having a shoulder engaged by anyof said keys on its manipulation for turning said key part from lockingregister with any of said grooves.
 19. Teaching apparatus as in claim 1,having provisions for visually associating said keys with the respectiveanswers to the question on each displayed element.
 20. Teachingapparatus as in claim 19, in which said provisions are differentdistinguishing marks on said keys corresponding to the same marks on therespective answers to the question on each displayed element.